DE1493839B1 - Process for the preparation of tertiary amines - Google Patents

Description

The invention relates to an embodiment of the method according to patent 1,288,611 for production of tertiary amines by hydrogenation of N, N-disubstituted monocarboxamides at increased '' Pressure and at temperatures between 200 and 350 ° C in the presence of copper chromite as a catalyst, which is characterized in that N, N-disubstituted carboxamides of the general formula

R — C — N

Il ο

15th

in which R is a hydrocarbon radical with 7 to 21 carbon atoms and R ₁ and R _{2 represent} identical or different, straight-chain or branched alkyl radicals with 1 to 8 carbon atoms or cycloaliphatic or aliphatic radicals, which in turn can be substituted by hydroxyl or ether groups, in hydrogenated the gas phase in the absence of solvents with at least a 50-fold excess of hydrogen. The tertiary amines, the structure of which corresponds to the acid amides used, are obtained in very good yields without any significant formation of by-products.

It has now been found that good yields of tertiary amines are also obtained if the Amides hydrogenated in the presence of inert solvents.

Inert solvents are those that do not undergo any chemical changes under the prevailing reaction conditions suffer e.g. B. ethers or hydrocarbons. Saturated or aliphatic are preferred cycloaliphatic hydrocarbons such as gasoline, dimethylcyclohexane or decahydronaphthalene are used. You can also use unsaturated hydrocarbons - on their own or in a mixture with saturated ones Hydrocarbons - use because their simultaneous hydrogenation to saturated hydrocarbons generally does not bother.

The amount of solvent added is variable within wide limits and ranges from only a few percent up to a multiple, based on the acid amide used.

The following examples serve to further illustrate the process according to the invention. she show that the process can be carried out continuously with particular advantage. Of course however, a discontinuous procedure is also possible.

B e i s ρ i e 1 1

The reaction furnace of a continuously operating high-pressure hydrogenation apparatus, which in the usual way consists of a hydrogen heater, heat exchanger, separator bottles, gas circulation pump and liquid pump, was charged with 800 ml of a lumpy supported catalyst made of 25% copper chromite which was precipitated on 75% silica gel 250 atm and 280 ⁰ C per hour a mixture of 140 ml and 260 ml Stearinsäuredimethylamid Dekyhydronaphthalin and 4 Nm ³ hydrogen passed.

After letting down the reaction mixture and distilling off the solvent, the crude tertiary amine fractionally distilled. Pure octadecyldimethylamine was used in the boiling range from 145 to 150 ° C obtained in an amount of 75% of theory.

Example 2

Under the same working conditions as described in Example 1, the reaction furnace was filled with 800 ml of copper chromite catalyst according to A dki η s in the form of 4 mm tablets, a mixture of 200 ml of gasoline and 100 ml of myristic acid dimethylamide and 4 Nm ^{3 of} hydrogen were passed after the catalyst had previously been heated to 250 ° C. in the hydrogen cycle until the water separation had ended.

After letting down the reaction mixture and distilling off the solvent, the crude tertiary amine fractionally distilled. This was tetradecyldimethylamine, bp., 105 to 110 ° C, in one Received amount of 72% of theory.

Example 3

Analogously to the conditions of Example 1, coconut fatty acid dimethylamides were used instead of 1 Vh per hour a mixture of 0.5 1 coconut fatty acid dimethylamide and 0.5 1 dimethylcyclohexane is fed into the system.

After letting down the reaction mixture and distilling off the dimethylcyclohexane, the obtained crude alkyldimethylamine fractionated in vacuo. Kokosalkyldimethylamin was in a Amount of 73% of theory obtained, bp = 40 to 160 ° C.

The inventive method offers the advantage of an easier and faster transfer of the Acid amides in the gas phase. It is therefore particularly suitable for the hydrogenation of long-chain monocarboxamides.

Claims (1)

Claim: Process for the preparation of tertiary amines by hydrogenation of N, N-disubstituted carboxamides the general formula R — C — N ο ^K in which R is a hydrocarbon radical with 7 to 21 carbon atoms and R ₁ and R _{2 represent} identical or different, straight-chain or branched alkyl radicals with 1 to 8 carbon atoms or cycloaliphatic or aliphatic radicals, which in turn can be substituted by hydroxyl or ether groups, at elevated pressure and at temperatures between 200 and 35O ° C in the gas phase with at least a 50-fold excess of hydrogen in the presence of copper chromite as a catalyst according to Patent 1288 611, characterized in that the amides in the presence of inert solvents, preferably in the present hydrogenated of saturated aliphatic or cycloaliphatic hydrocarbons. ORIGINAL INSPECTED